High-resolution observations of a dual-core anticyclonic eddy in the Algerian Basin (PROTEVS-MED 2016)

mesoscale dynamics in the mediterranean sea have been investigated for years and anticyclonic eddies are regularly observed features in the algerian basin. in early spring 2016, a field experiment during the protevsmed 2016 cruise thoroughly investigated this specific eddy, when it was located near the north balearic front, taking high-resolution (seasoar) hydrological transects, several ctd casts and ladcp measurements. in addition, four drifting buoys were released in the eddy core. these in situ measurements revealed that the vertical structure of this anticyclone was made of two water lenses of very different origins (atlantic water above and western intermediate water below) spinning together. in the vicinity of the north balearic front, which may act as a dynamical barrier for structures, the eddy interacted with a subsurface anticyclonic eddy made of modal water, which fostered cross-front exchanges generating filaments by stirring. the high-resolution sampling revealed fine scales structures both adjacent to the eddy and within its core.the eddy has been targeted from 21 march to 1 april 2016 taking advantage of a meteorological window. it has been sampled with: a towed undulating vehicle, the seasoar designed and built by chelsea instruments; it gets mounted on its sides two sea-bird sbe-9 (sbe 3 temperature and sbe 4 conductivity sensors) and a wetlabs fluorometer of type chloroa wetstar ctd casts performed with a sea-bird sbe-9 (sbe 3 temperature and sbe 4 conductivity sensor) and an rdi 150 khz current profiler mounted in a general oceanics 12-place rosette, with12l niskin bottles drifters with holey-sock positioned at 50 m deep below the expected ekman layer thickness (remaining in the eddy until mid may).

地中海中尺度动力学已研究多年，反气旋涡旋是阿尔及利亚盆地中常见的观测特征。在2016年春季初，在Protevsmed 2016航次期间进行的一项现场实验，对该特定涡旋进行了深入探究，当时它位于北巴利阿里海锋附近，进行了高分辨率（SeaSoar）水文横切，进行了多次CTD投放和LADCP测量。此外，在涡旋中心释放了四个漂流浮标。这些现场测量揭示了该反气旋的垂直结构由两种来源极为不同的水层组成（上方为大西洋水，下方为西中水）共同旋转。在北巴利阿里海锋附近，该锋可能作为动态屏障，涡旋与由模式水构成的次表反气旋涡旋相互作用，促进了越锋交换，通过搅拌生成细丝状结构。高分辨率采样揭示了涡旋周边及其核心区域的精细尺度结构。该涡旋在2016年3月21日至4月1日间被选定研究，利用了气象窗口。研究采样包括：由切尔西仪器设计制造的SeaSoar拖曳波动车，其两侧安装有两个Sea-Bird SBE-9（SBE 3温度和SBE 4电导率传感器）和一个Wetlabs氯荧光计Chloro-a WetStar；使用Sea-Bird SBE-9（SBE 3温度和SBE 4电导率传感器）和安装在通用海洋学12点罗盘中的RDI 150 kHz流速剖面仪进行的CTD投放，以及带有12升Niskin瓶的投放；在预计的Ekman层厚度以下50米深处的孔洞袜漂流器，漂流器保持在涡旋中直至5月中旬。